Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Assets:
Investments	$ 2,804	$ 26,213
Total assets at fair value	2,804	26,213
Fair Value, Inputs, Level 2
Assets:
Investments	2,804	25,311
Total assets at fair value	2,804	25,311
Fair Value, Inputs, Level 3
Assets:
Investments		902
Total assets at fair value		$ 902